They say they cannot return to their communist homeland because they risk being tortured or killed by the Laos military – claims rejected by Laos officials.
The refugees, including men, women and children, had hoped to march 350 km to the capital, Bangkok, to plead with the United Nations for help.
But they were blocked after walking less than 10km by a barrier of Thai police and soldiers.
Several sources have told Al Jazeera that about 30 Hmong were injured in a confrontation with the Thai authorities.
|The refugees say they have been treated as prisoners for the past four years
The Hmong say they have been living like prisoners for the past four years.
They have staged a series of hunger strikes and several have threatened to kill themselves, but their pleas have gone largely unnoticed.
Last month several huts in the camp were burned down after the refugees were told they would not be resettled in the United States.
The Thai government recently signed an agreement with Laos to send more than 7,000 Hmong back home, saying they are illegal migrants.
It has barred the UN refugee officials from entering the camp to issue refugee certificates.